[Effect of gamma-radiation on the activity of proteases associated with spleen and brain nuclear histones of young and old rats].

It has been found that proteases specifically splitting histones are associated with histones from spleen and brain nuclei of 4- and 26-month-old rats. The activity ofproteases isolated together with histones increases after irradiation of rats with 10 Gy The activation degree of these proteases depends on the animal age and postradiation period. Activation ofhistone-associated proteases by means of gamma-radiation is more pronounced in spleen nuclei from old rats than from the young ones.

[Study of DNA-binding proteins of rat liver mitochondria].

Acid-soluble proteins able to form DNA-protein complexes in the presence of physiological concentration of NaCl were isolated from rat liver mitochondria. Electrophoretic analysis of these proteins in 15% polyacrylamide gel showed that mitochondrial acid-soluble proteins include of approximately 20 polypeptides with molecular weight of 10-120 kDa. The fraction of acid-soluble proteins can be separated into basic and acidic proteins by chromatography on DEAE cellulose.

DNA-binding proteins of mammalian mitochondria.

Acid-soluble proteins were isolated from liver and spleen mitochondria and their ability to form complexes with DNA was investigated. According to electrophoresis data, acid-soluble proteins include about 20 polypeptides ranging in the molecular mass from 10 to 120 kDa. It was found that acid-soluble proteins form stable DNA-protein complexes at a physiological NaCl concentration.

[Study of DNA-binding proteins in mitochondria of rat liver gamma-irradiation].

Acid-soluble proteins were isolated from the liver mitochondria of control and irradiated (8 Gy) rats. By means of electrophoresis in 15% polyacrylamide gel, these proteins were separated into more than 20 polypeptides of molecular masses between 10 and 120 kDa. The irradiation of rats with a dose of 8 Gy led to changes in the polypeptide content of mitochondrial acid-soluble proteins in the postradiation period.

[Effect of gamma-radiation and mitochondrial apoptogenic factors on nuclear protease activity].

An increase in protease activity was shown in thymus nuclei of rats exposed to gamma-radiation. The activation of histone-specific proteases depended on the duration of postradiation period. Also, it was revealed that incubation of thymus nuclear with the intermembrane fraction of liver mitochondria caused degradation of histones and nonhistone nuclear proteins, as well as internucleosomal fragmentation of DNA.

Involvement of proteases in apoptosis.

Genetically programmed (apoptotic) cell death plays a key role in cell and tissue homeostasis and in pathogenesis of various diseases. However, the mechanisms involved in apoptotic cell death are poorly understood. At present, the role of proteases in key events of apoptosis is intensively studied and discussed and the involvement of various proteolytic enzymes in the induction and development of the cell death is well-recognized.

Study of protein carbonyls in subcellular fractions isolated from liver and spleen of old and gamma-irradiated rats.

Age- and gamma-irradiation-dependent accumulation of oxidatively modified proteins (measured as carbonyl level) was studied in cytoplasm, mitochondria and nuclei isolated from spleen and liver of 4- and 26-month-old rats. The protein carbonyl levels significantly increased with age in all fractions studied. The carbonyl content was found to be two times higher in the nuclei than in the mitochondria and cytoplasm, which may be related to an extensive modification of lysine and arginine residues in histone molecules.

Gamma irradiation or hydrocortisone treatment of rats increases the proteinase activity associated with histones of thymus nuclei.

An increase in the activity of histone-associated rat thymus nucleus proteinases specific for histones H2A, H2B and H1 was shown after gamma irradiation or hydrocortisone treatment of animals. Histone H1-specific proteinase activity is dependent on DNA and increases in the presence of denatured DNA, whereas proteinases specific for core histones are inhibited in the presence of denatured DNA. The increase in the activity of histone-associated proteinases depends on the radiation dose and the time after irradiation or hydrocortisone injection.

[Hydrocortisone and partial hepatectomy activate a proteinase associated with histones].

Proteinase activity has been shown to be associated with histones of rat thymus and liver nuclei. Hydrocortisone increases the activity of proteinases associated with thymus nuclear histones. Increasing activity of histone-associated proteinases is also observed during intensive transcription and replication in regenerating rat liver.

[Association of proteinases with histones from rat thymus nuclei].

Histone H2A, H2B, and H1--specific proteinases tightly associated with histones were shown to be present in rat thymus nuclei. The activity of proteinases tightly associated with histones increases after exposure of animals to gamma-rays. The denatured DNA activated the histone H1-specific proteinase.

Gamma-irradiated DNA activates histone H1-specific proteinase of rat liver nuclei.

We investigated the effect of various forms of DNA (double- and single-stranded calf thymus DNA, circular plasmid DNA, gamma- and UV-irradiated DNA and DNAase I-treated double-stranded DNA) aggregated with histones, on the proteolysis of these histones by proteinase associated with the rat liver nuclear scaffold. It was shown that the nuclear scaffold-associated proteinase is able to degrade selectively the histone H1 only in the presence of the DNA containing single-strand breaks induced by gamma-radiation or DNAase I treatment as well as in the presence of heat-denatured DNA. This proteinase is not activated by the double-stranded circular plasmid DNA or by UV-treated double-stranded DNA.

[DNA and nucleotide triphosphate-activated proteinase from rat liver nuclear matrix specific for H1 histone].

The action of DNA and nucleotide phosphate on histone hydrolysis by nuclear matrix preparations from rat liver has been studied. It is shown that proteinase specific for H1 histone is associated with the nuclear matrix. This proteinase is activated by denatured DNA and by DNA treatment with DNase I or gamma-irradiation, but it is not activated by UV-irradiated DNA.

[Protease activity of the nuclear matrix of rat hepatocytes].

It was demonstrated that the nuclear matrix of rat liver possesses the protease activity. The specific activity of nuclear matrix proteases exceeds that of intact nuclei 7-fold. The optimum activity of nuclear matrix proteases is observed at pH 8-9.

[Postradiation activation of proteinases associated with the hepatocyte nuclear matrix in rats].

Proteinase activity of the nuclear matrix of rat hepatocytes was 7-8-times as high as that of initial nuclei. Activity of nuclear matrix proteinases was optimum at pH 8-9. Proteolytic activity associated with the nuclear matrix, increased by 1.

[Change in the initiation of DNA synthesis on the nuclear matrix and its DNA-protein composition in gamma-irradiated hepatoma cells].

It was shown that gamma-irradiation of Zajdela hepatoma cells (10 Gy) induces inhibition of DNA synthesis initiation at a nuclear matrix and a change in its DNA-protein content. Irradiation of hepatoma cells with 10 and 50 Gy decreases incorporation of newly synthesized proteins in the firmly bound DNA-protein complexes of nuclear matrix. After 60-120 min postirradiation incubation of cells at 37 degrees C DNA-protein content of the nuclear matrix and its firmly bound DNA-protein complexes are restored.

[Reorganization of the protein composition of the nuclear matrix of hepatoma cells after inhibition of DNA synthesis with novobiocin].

The nuclear matrix of Zajdela hepatoma cells, in which DNA synthesis was blocked by novobiocin, contained 2.5-3.0 times more DNA and protein not dissociating in 2 M NaCl than the nuclear matrix of control cells.

[Action of low-molecular compounds of a polyphenol-quinoid nature from an irradiated organism on cytochrome C].

It was shown that gamma-radiation-induced oxidation of phenol compounds in the animal liver, which leads to o-dioxyphenols and quinones accretion, is one of the reasons for excluding cytochrome c from the respiratory chain of mitochondria. Radiochemical oxidation of tyrosil groups at the protein site of cytochrome c and, as a result, the restriction in the rate of reduction of the latter were noted. On the basis of the data obtained the authors discuss the mechanism of weakening the coupling of oxidation to phosphorylation upon irradiation and the molecular mechanism of the so-called cytochrome effect.

[DNA-protein complexes of the nuclear matrix of Ehrlich ascites carcinoma cells].

A DNA-protein complex resistant to 8 M urea and 0.1% SDS was obtained by chromatography of nuclear matrix lysate from Ehrlich ascite carcinoma cells on Sepharose 2BCL. Separation of the complex under more severe conditions (4 M guanidine hydrochloride, 5 M urea) on hydroxylapatite resulted in protein and DNA fractions, as well as in two fractions of the DNA-protein complex.